The American Printer: A Manual of Typography / Containing practical directions for managing all departments of a printing office, as well as complete instructions for apprentices; with several useful tables, numerous schemes for imposing forms in every variety, hints to authors, etc.

by Thomas MacKellar

< or ⫎ are signs of minority,—when we would denote that a is less than b.

∞ is the character of similitude used by Wolfius, Leibnitz, and others. It is used in other authors for the difference between two quantities when it is unknown which is the greater of the two.

∷ so is. The mark of geometrical proportion disjunct, and is usually placed between two pair of equal ratios: as, 3∶6∷4∶8 shows that 3 is to 6 as 4 is to 8.

∶ or ∴ is an arithmetical equal proportion: as, 7.3∶13.9; i. e. 7 is more than 3, as 13 is more than 9.

⬜ quadrate, or regular quadrangle,—viz. ⬜AB=⬜BC; i. e. the quadrangle upon the line AB is equal to the quadrangle upon the line BC.

△ triangle: as, △ABC=△ADC.

∠ an angle: as, ∠ABC=∠ADC.

⟂ perpendicular: as, AB⟂BC.

▭ rectangled parallelogram, or the product of two lines.